Gas springs may be utilized to yieldably resist movement of a body, such as a clamping ring for a metal blank of a die in a press for forming sheet metal parts. The springs are generally constructed with an actuating rod connected to a piston slidably received in a cylinder having a chamber charged to a predetermined pressure with an inert gas, such as nitrogen. This provides a spring effect or cushion permitting the rod to yieldably move towards its retracted position when a force applied externally to the rod exceeds the opposing force produced by the gas in the chamber acting on the piston. The gas springs can be operated with an external source of gas or can be pre-charged and operated as a self-contained unit.
A valve received in a gas fill passage through the cylinder selectively communicates the chamber filled with pressurized gas with the exterior of the cylinder. The valve permits the compressed gas to be removed from the chamber when desired, enables the addition of compressed gas to the chamber and prevents the gas from leaking from the chamber when it is desired to maintain the pressurized gas in the chamber. Conventional valves used with gas springs have an intricately shaped body with a generally frusto-conical or tapered side wall portion which is constructed to mate with a complementary frusto-conical tapered portion of the gas fill passage in the cylinder to provide a seal between the valve and the cylinder to prevent leakage of the gas from the chamber. Due to the small size of conventional filler valves and the intricately shaped gas fill passage required with these valves, it is extremely difficult to accurately machine the gas fill passage to provide a sufficient seal between the tapered portions of the valve and the cylinder. Further, any scratching or scuffing of the tapered portion on the valve body or in the fill passage compromises or destroys the seal between them and requires replacement of the valve or the entire cylinder body.
Additionally, conventional valves have a threaded brass swivel which is rotatable relative to the valve body to permit the swivel to be rotatably received in complementary threads in the gas fill passage while the valve body is slidably engaged with the interior of the gas fill passage, substantially without rotation of the valve body, to prevent damage to the valve body as it is assembled into the fill passage. The brass swivel is fragile and can be over-torqued when the filler valve is assembled into the gas fill passage thereby jamming or distorting the brass swivel such that the filler valve cannot be removed from the fill passage without damaging it. Further, the brass swivel has a small number of very small threads which may be easily damaged or stripped when assembled into the fill passage, thereby destroying the valve and making it very difficult, if not impossible, to remove the filler valve from the fill passage.